Here is what the letter says, in part via David Codrea:
We are writing to express our serious concerns about the Administration's response to investigations of the Bureau of Alcohol, Tobacco, Firearms and Explosives' (ATF) "Project Gunrunner" and is offshoot known as "Fast and Furious."There has been significant movement on this scandal since it was first reported months ago. This is definitely a sign that some inertia is building.
Reports of the tactics used in this operation are extremely troubling. The ATF allegedly encouraged gun store owners to sell thousands of fireams to customers whom store employees considered suspicious. Our concerns were heightened with news that one of the firearms sold may have been used in the murder of a Border Patrol agent. These allegations call into question the judgment of the agents involved. It is equally troubling that the Department of Justice has delayed action and withheld information from Congressional inquiries.
Read entire letter.